1. Field of the Invention
This invention relates to the field of digital communication systems, and particularly to addressing schemes for such systems.
2. Description of the Related Art
Many systems exist for transferring data between peripheral devices and a master device such as a microprocessor. Such systems typically employ a multiple-wire bus structure to which each device is connected, with data transferred between devices either serially or in parallel. To retrieve data from a particular device on the bus, the device must first be addressed or enabled in some fashion. Systems of this type include the SMBus and i2c bus systems.
However, such systems require each device to have a unique address or unit number that is configured in hardware. This can be expensive, as it requires each device to have the necessary hardware interface (e.g., dedicated I/O pins on the device). These costs can be unacceptably high, particularly for simple devices that would otherwise be small and inexpensive.
Another addressing approach is found in a system known as the serial peripheral interface (SPI). The SPI is a full duplex, four wire synchronous serial interface based on a master/slave relationship. However, the SPI requires that each interconnected device have a pin by which the device is enabled prior to transferring data; this increases processing overhead and the system's I/O requirements. The system also requires 4 wires, which may consume more area than is desired.